Lou Henry Hoover (March 29, 1874 – January 7, 1944) was the wife of President of the United States Herbert Hoover and served as First Lady from 1929 to 1933.

Marrying her engineer husband in 1899, she traveled widely with him, including to Shanghai, China, and became a cultivated scholar and linguist. A proficient Chinese speaker, she is the only First Lady to have spoken an Asian language. She oversaw construction of the presidential retreat at Rapidan Camp in Madison County, Virginia. She was the first First Lady to make regular, nationwide radio broadcasts to the American public.

Lou Henry grew up in Iowa and California. She enrolled at Stanford as its only female geology major in 1894. There she met future president Herbert Hoover. They married after her graduation and she accompanied him to China where he worked as a civil engineer.